From the HN guidelines:

Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.

I'm not sure what you're implying, because both interpretations are valid to downvote.

I'm saying that this statement especially when your "question" is an argument hidden behind a question mark, is not consistent with the suggestion to "assume good faith" espoused in the guidelines.

Ah, I see.

I will note that people make arguments via questions pretty often in normal conversation, so that's not necessarily an accusation of significant bad faith. It could be more of a complaint about rhetorical technique.

But let's treat it as an accusation of bad faith. In that case, we have a deeper issue. Assuming that it's a real question asked in good faith is actually the weakest plausible interpretation, because the link makes it a self-disproving theory. Honestly the tongue-in-cheek interpretation is probably the strongest one.

There's no way to treat it as a strong argument and as a real question asked in good faith.

Also it can be okay to downvote misinformation even when the commenter didn't do anything wrong.

I guess I was being charitable, and imagining that the poster might be a Korean of a certain age where this myth held weight. The article suggests that young Koreans have changed attitudes, but that doesn't mean that everyone has. I think the comment replies to his question did a fine job challenging the myth. Obviously it's just my opinion, but I'd rather save downvotes for people who were clearly trolling or maliciously off-topic (and I don't see that here).

To be clear, I didn't downvote their comment — I don't think it warranted it — I'm just saying I can sympathise with the argument that a comment that doesn't add anything useful to the discussion is a fair target for a downvote.

Saying "But what about x?" when you yourself provide a link that says that X is a non-issue doesn't make for an engaging discussion. "But what about x? This link suggests it's not a problem but I think it is because of y" does make for an engaging discussion, even if y is seemingly nonsense.

That's a fair point. Thanks for the respectful conversation about this. :)

Even if the person turns out to be exactly as you've described, I think that they will have the resilience to overcome these devastating downvotes.

Maybe this person could even use the downvotes as a signal that there is something seriously wrong with their belief and learn something new.